tank level monitoring guide · 2021. 4. 22. · 2 / tank level monitoring guide tank level...
TRANSCRIPT
USING SENIX ULTRASONIC LEVEL SENSORS
Tank Level Monitoring Guide
2021
2 / Tan k Le ve L Mo niToring guide Tank Leve L MoniToring guide / 3
Tough
Smart
Connected
The Tank Level Monitoring System Market is expected to continue to grow and is driven by various factors such as, reduction
in usage of carbon fossils fuels, regulation and policies for clean energy and low installation cost. In addition, the Dry/
Bulk material market is also growing. For example, for the purposes of this Senix Guide, silos with grain and other solids or
powders, container of materials such as plastics, sand, cement, and food types are considered Tank Level Measurement.
The purpose of this guide is to summarize Senix’s sensors, accessories and sensor systems for Tank Level Monitoring and
Measurement, and to provide help and guidance in optimizing your ultrasonic sensors and accessories for Tank Level
applications. Senix products are Tough. Smart. Connected
• Built in 316 stainless steel housing (except PVC models)
• Offer ruggedized piezoelectric ultrasonic transducer
• Built with hardened & protected solid state electronics
• Include UV resistant, potted-in, PUR-jacketed cable
• Designed with short and overload protected outputs
• Have an IP68 ingress rating
• Easily connect with your equipment
• Optimize the sensor to the application
• Create stand-alone functions
• Duplicate applications without re-calibration
• Ready out of the box but fully adjustable with free SenixView Software
with nearly 80 sensor parameters that can be optimized
• Connect To PLCs, pumps, motor drives, displays, alarms, lights & more
• Multiple simultaneous industry standard outputs that are selected
using SenixVIEW software including analog outputs, sourcing, or
sinking switches, and either RS-485 or RS-232 serial communications
• All configurable to the applications needs
• Choose RS-232 or RS-485 by sensor part number
• Multi-sensor Modbus-addressable RS-485 networks
• Wireless connectivity with Senix AirWire LoRa technology
• Monitor at Senix LiquidLevels.com or with other Cloud-based software
Tank Level MonitoringTank Level Monitoring
Introduction
What is a Tank Level Monitoring System?
Ultrasonic Sensors
Growing Demand
The Senix 3-Step Process for Tank Level Measurement
Step 1 – Select the Right Sensor
General Purpose Sensors
ToughSonic CHEM Sensors
Step 2 – Accessories and Components
Displays & Controllers
Mounting Options
Wireless Connectivity
Senix AirWire Wireless LoRa
Cloud-based Monitoring
Step 3 – Optimizing the Sensor for Your Application
SenixVIEW Software
Senix Ultrasonic Sensor FAQS
Tank Foam, Turbulence and Condensates
Multi-Sensor Set-up
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Table of Contents
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With over 30 years of experience, Senix offers a full range of Ultrasonic sensors, accessories, and communications options for Tank Level Monitoring applications.
• NON-CONTACT – NOTHING TOUCHES THE SAMPLE OR TARGET
• EASY TO INSTALL AT THE TOP OF THE TANK INTO STANDARD FITTINGS
• USE INDOORS OR OUTSIDE, IN METAL OR PLASTIC TANKS
• CONNECTS TO OTHER INDUSTRIAL EQUIPMENT
• MEASURES A WIDE VARIETY OF LIQUIDS AND LIQUID ENVIRONMENTS
• CAN HANDLE MANY DRY/BULK MATERIALS SUCH AS SOLIDS, POWDERS, GRAINS, ETC.
• ACCESSORIES TO DISPLAY, ALARM AND CONTROL LIQUID LEVELS
• WIRELESS OPTION SENDS TANK LEVELS TO A LAN OR THE CLOUD
• MRO & OEM TANK SETUP DUPLICATION WITHOUT RE-CALIBRATION
• INVENTORY
• BATCH CONTROL
• LOW AND HIGH-LEVEL ALARMS
• EMPTY, FILL OR MAINTAIN LEVEL
• PUMP & VALVE CONTROL
Senix ToughSonic ultrasonic level sensors offer advantages
over other sensor types:
Applications
Senix sells to end-users, resellers, and OEMs (Original Equipment Manufacturers)
in many industries. Standard ultrasonic sensor products provide solutions for
most new or retrofit applications. Senix also will offer custom sensor designs
to meet special packaging or design requirements. We also will configure our
flexible and versatile ToughSonic sensors into packaged systems for object
detection, remote mounting locations for level applications, or for a wide array
of system needs.
A Tank Level Monitoring System is
an advanced system that is used for
measuring and monitoring the level
of material inside atmospheric tanks.
There are different principles that can
be selected for Tank Level Monitoring
depending on the types of material in
the tank, accuracy required and other
factors. Tank level monitoring systems
have a wide range of applications in
different industries such as oil & fuel,
power plant, mining, automotive,
farming, food and beverage, and
more. Rising demand for safety and
efficiency requirements among
numerous process industries have
boosted the growth of the tank level
monitoring market.
The Senix Tank Measurement Guide
will focus on ultrasonic sensors and
accessories. Senix Corporation is a
high-tech engineering, manufacturing,
and sales company nestled in the town
of Hinesburg in the scenic foothills of
the Green Mountains of Vermont. Since
1990, Senix has been the example of
Yankee ingenuity, continually improving
products and serving a gradually
increasing number of customers around
the world. Senix designs, manufactures,
sells, and supports a wide range of
perhaps the most tough and rugged
ultrasonic distance and level sensors
available today. The free SenixVIEW
software makes Senix ToughSonic
sensors the most versatile and flexible
sensors as well.
Non-contact ultrasonic sensors from
Senix have distinct advantages in
challenging environments where
corrosive, scaling, coating, or dirty
materials are likely to negatively
impact the performance and
maintenance costs of contact sensors.
Non-contact ultrasonic sensors are
also desirable where the material
being measured cannot be corrupted
by contact with a measuring device.
Ultrasonic sensors are used to
measure distance to a remote object
through the air without touching it. In
addition to Tank Level Measurement
applications, our sensors are used
in a broad array of industrial and
scientific applications, distance
measurement including machine
and motion controls, web controls
(material loop and roll diameter),
liquid level measurement, water
measurement and control such as in
farming and agriculture applications—
virtually any place where non-intrusive
measurement and feedback are
desired.
Senix non-contact ToughSonic®
ultrasonic sensors offer cost-effective,
continuous level measurement for
small and large tanks. They install
at the top of the tank, are not
immersed in the liquid or what is being
measured, and can measure water and
benign liquids, most chemical liquids,
as well as solids, some powders, and
other materials. Senix SafeSonic
sensors are intrinsically safe sensors
for hazardous areas.
What is a Tank Level Monitoring System?
Tank Leve L MoniToring guide / 7 6 / Tan k Le ve L Mo niToring guide
Ultrasonic Sensors The Growing DemandUltrasonic level measurement with Senix ToughSonic Sensors provides continuous, non-contact and maintenance-free level
measurement of fluids, pastes, sludges, and coarse bulk materials. An ultrasonic measurement is unaffected by dielectric
constant, density, or humidity. Senix non-contact ToughSonic® ultrasonic sensors offer cost-effective, continuous level measu-
rement for small and large tanks.
Ultrasonic sensors measure the distance
to or presence of a target object or
material through air without touching it.
The measured distance is provided as an
output in a variety of standard electrical
interfaces compatible with displays,
machinery, PLC’s, computers and most
electronic or electrical machinery.
Knowing the speed of sound, the sensor
determines the distance of the target
and sets its outputs accordingly. There
are several advantages of ultrasonic
technology, and specific advantages of
Senix’s ultrasonic sensor technology.
Sensor outputs are set based on the
measured distance, or under override
conditions, a lack of target detection or
user-selected response algorithms.
Outputs can be:
• An analog voltage or current signal
proportional to the measured
distance
• Switches or relay contact closures that
open or close at specific distances
• Distance data transmitted as serial
data communications.
What do Senix® ultrasonic sensors do?
Senix ultrasonic technology differs
from medical ultrasonic. The ultrasonic
frequency used for level or distance
cannot go through tank walls, or
measure thickness such as with an
NDT type sensor. Since an ultrasonic
signal is sound based, it will not work
in a vacuum environment. Ultrasonic
signals are not usually measured at very
high repetition since the speed of sound
is the limiting factor. The fastest Senix
rate is 200 Hz with a maximum working
distance of about 24 inches.
Ultrasonic sensors are well-suited
for most tank or container level
measurements. They will detect both
large and small targets, including
liquids, solids, and granular materials.
The size, shape, orientation, and
composition of the target will affect
the maximum distance at which it
can be detected. The sensor is not
affected by optical characteristics such
as color, reflectivity, transparency, or
opaqueness.
From Industries
From IoT Technology
Increasing demand for tank level
monitoring systems to meet safety and
efficiency requirements, especially from
the process industries, such as chemical
plants, pulp & paper, steel mills, power
generation, and glass manufacturing,
is expected to boost the overall growth
of the tank level monitoring system
market.
Tank overfills result in material and
production loss while threatening
to damage the silo itself. For tanks
containing hazardous materials,
spilling could also lead to disastrous
environmental impacts and associated
cleanup costs and fines. Failing to refill
feedstock tanks in time could also
cause businesses to run out of stock,
which leads to delayed production
and delivery. This is one of the major
reasons behind the adoption of tank
level monitoring systems.
With the growing wireless technology
market that allows for remote
monitoring, there is an increasing
interest from customers to add tank
level monitoring systems, as well as to
monitor them remotely. Sensors and
sensor systems can communicate via
cellular, satellite, or the rapidly growing
LoRa technology.
The following tables summarize Senix ToughSonic General Purpose and CHEM sensors for:
Maximum Range: The longest distance each sensor can measure
Optimum Range:
When selecting a sensor, it is advisable not to select a sensor at the very edges of the desired
measuring range. For example, when wanting to measure anything that might get close to 14 ft.,
it is advisable to select the next sensor range up rather than risk having a measurement need at
the fringe of the range of the sensor.
Dead Band:
Objects that are too close to the transducer may return the echo before the transducer is ready
to receive it. The minimum working distance is the dead band. The dead band is larger for
sensors with greater sensor measurement range
Based upon desired measurement range, and the chemical characteristics of the target being measured, Senix has a sensor
for all types of tank applications.
8 / Tan k Le ve L Mo niToring guide Tank Leve L MoniToring guide / 9
Step 1Select the Right ToughSonic Sensor for Your Application
Selecting the Right Sensor
Accessories & Components
Optimizing Your Sensor
The Senix 3-Step Process for Tank Level Measurement
The right sensor range for your
application can be selected based
on target or working range, target
characteristics, measurement
environment, and tank size. In liquid
level applications, we recommend that
you select a sensor range at least 25%
greater than the maximum distance you
are likely to measure. When measuring
dry materials or difficult targets, we
recommend selecting a sensor range at
least 50% greater than your maximum
measurement distance.
Senix has sensors than can measure
just over 15 meters (about 50 feet)
and varies by model. The distance at
which an object is detected depends
on its size, shape, composition, and
orientation. In general, the target must
be larger to be detected at longer
distances – the object must reflect a
sufficiently strong ultrasonic echo back
to the sensor to be detected.
For General Purpose sensors and
applications, Senix offers its
ToughSonic 3, ToughSonic 12,
ToughSonic 14, ToughSonic 30 and three
different models of it ToughSonic 50.
The number “3” in ToughSonic 3, is the
maximum distance measured in feet.
Some common chemicals can damage
or corrode sensor materials, even 316
stainless steel. Transducer elements and
bonding adhesives are also susceptible.
ToughSonic CHEM sensors expand the
range of environments in which our
sensors operate.
The ToughSonic CHEM sensors
avoid these problems by using a
continuous injection molded housing of
Polyvinylidene fluoride (PVDF), a highly
non-reactive thermoplastic that resists
solvents, acids, and hydrocarbons.
ToughSonic CHEM sensors have both
top and bottom mounting threads and
include a potted-in, PUR-jacketed, UV
resistant cable. Verify your chemicals
and operating temperatures with this
compatibility chart. Where resistance
to chemical exposure is required,
Senix offers its Tough Sonic CHEM 10,
ToughSonic CHEM 12, ToughSonic
CHEM 20 and ToughSonic CHEM 35
sensor for environments that require
chemical compatibility.
Large, flat targets such as a liquid
surface in a tank are detected at the
maximum range. Curved objects or
sound absorbing materials such as
fabrics or non-wovens reflect less
energy directly back to the sensor.
Granular materials may absorb sound
or deflect sound energy away from the
sensor due to surface variation and/or
angle of repose. Sensor maximum range
should be de-rated for these targets.
Other factors affect how close an
ultrasonic sensor can be to a target and
still measure distance correctly. When
too close the sensor will not detect the
first echo, but may detect a second or
third echo, yielding a longer than actual
value. This dead band distance varies
by model and is larger for longer range
models, varying from 44 to 305 mm
(1.75 to 14 inches). The minimum range
and maximum range define the limits of
the material window, which is the useful
operating range of the sensor. The
material window is user adjustable with
SenixVIEW software to ignore unwanted
targets or optimize system performance.
When used outdoors we recommend
limiting the range to the sensor’s
“Optimum Range” specification rather
than the “Maximum Range” to allow for
environmental extremes.
10 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 11
General Purpose Sensors ToughSonic CHEM Sensors
Senix Product Line Summary
Ranges
3 Ft. 14 Ft. 30 Ft. 50 Ft. 50 Ft. 50 Ft.
ToughSonic 3 ToughSonic 14 ToughSonic 30 ToughSonic 50 (rear mount)
ToughSonic 50 (clamp mount)
ToughSonic 50(front & rear mount)
Max. Range
3 ft. (91 cm)
Max. Range
14 ft. (4.3 m)
Max. Range
30 ft. (9.1 m)
Max. Range
50 ft. (15.2 m)
Max. Range
50 ft. (15.2 m)
Max. Range
50 ft. (15.2 m)Optimum Range
1.75 to 24 in
(4.6 - 61cm)
Optimum Range
4 in to 10 ft
(100mm - 3m)
Optimum Range
10 in to 20 ft
(25.4 cm - 6.1 m)
Optimum Range
1 ft to 33 ft
(30.5 cm - 10 m)
Optimum Range
1 ft to 33 ft
(30.5 cm - 10 m)
Optimum Range
1 ft to 33 ft
(30.5 cm - 10 m)
Deadband < 1.75 in Deadband < 4 in Deadband < 10 in Deadband < 1 ft Deadband < 1 ft Deadband < 1 ft
Features
• 316 Stainless Steel
• Available in either
30mm or 1" NPT
threads (w/o nuts)
• R5232 orR5485
• 6 Wire Sensor
- Power
- Serial Interface
- 2 Configurable
outputs
- Teach Button
• 316 Stainless Steel
• Available in either
30mm or 1" NPT
threads (w/o nuts)
• R5232 orR5485
• 6 Wire Sensor
- Power
- Serial Interface
- 2 Configurable
outputs
- Teach Button
• 316 Stainless Steel
• 1.5" NPT threads
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable
outputs
- Teach Button
• 316 Stainless Steel
• 1.5” NPT threads,
rear mount
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable
outputs
- Teach Button
• 316 Stainless Steel
• Clamp Mount
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable
outputs
• PVC
• 2.5" NPT threads,
front and rear
mount
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable
outputs
Ranges
10 Ft. 12 Ft. 20 Ft. 35 Ft.
ToughSonic CHEM 10 ToughSonic CHEM 12 ToughSonic CHEM 20 ToughSonic CHEM 35
Max. Range
10 ft. (3 m)
Max. Range
12 ft. (3.7 m)
Max. Range
20 ft. (6.1 m)
Max. Range
35 ft. (10.7 m)Optimum Range
4 to 80 in
(100 mm - 2 m)
Optimum Range
4 in to 10 ft
(100mm - 3m)
Optimum Range
8 to 156 in
(20 cm - 4 m)
Optimum Range
12 in to 25 ft
(30.5 cm - 7.6 m)
Deadband < 4 in Deadband < 4 in Deadband < 8 in Deadband < 12 in
Features
• PVDF
• 1.5" Parallel Universal threads
(bottom) and 1" NPT threads
(top)
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable outputs
• PVDF
• 1.5" Parallel Universal threads
(bottom) and 1" NPT threads
(top)
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable outputs
• PVDF
• 1.5" Parallel Universal threads
(bottom) and 1" NPT threads (top)
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable outputs
• PVDF
• 2" Parallel Universal threads
(bottom) and 1" NPT threads
(top)
• R5232 orR5485
• 9 Wire Sensor
- Power
- Serial Interface
- 5 Configurable outputs
Most Senix General Purpose Sensors
are made of 316 Stainless steel and
are extremely rugged. ToughSonic
CHEM sensors are made of PVDF and
excellent for chemical environments.
Most sensors have a threaded housing
for easy mounting. The Clamp Mount
ToughSonic 50 is designed to be
mounted with an optional clamp.
Senix sensors have an integrated 6-wire
or 9-wire cable and two to five outputs.
The 6-wire models have two outputs
that can be configured; choices include
voltage, 4-20 mA current, sourcing
switch or sinking switch.
The 9-wire models have five outputs,
including one voltage, two current, and
two switches. All sensors also have a
serial interface supporting Modbus RTU
and ASCII character streaming.
All Senix sensors are either of a 6-wire or
a 9-wire design and a range of outputs.
The 6-wire have 2 configurable outputs,
and a user can select from VDC or 4-20
mA output or select wither of those
as a sourcing or sinking switch. If no
analog output is required and on serial
output is used, then a user can select
both analog outputs to be switches.
The 9-wire sensor still has VDC and
4-20 mA as well as serial output, but
5 configurable outputs and therefore
additional sourcing or sinking switches
are available. All sensors are available in
Serial Only versions at lower cost. Serial
Only sensors have no analog outputs
or switches and include an integrated
4-wire cable.
Features – Material, Mounting & Outputs Power Requirements Cable & Terminations Tank Level Measurement in
Hazardous AreasAll ToughSonic sensors have an input
power requirement of 10-30 VDC
(typical 45 mA @24 VDC)
All Senix ToughSonic sensors include
potted in and protected PUR
jacketed cables. Standard cable
length is 6.5 ft., although other
lengths are available as a custom
sensor. All cables are shipped with
flying leads, however optional
connectors such as M12 and others
are available as options.
If your Tank Level Measurement
application is in a hazardous area and
requires an intrinsically safe sensor,
our SafeSonic 25-L is a two-wire,
4-20 mA, loop powered, intrinsically
safe sensor CSA approved for use in
hazardous areas only in the United
States and Canada.
12 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 13
Compared to wired communications,
a wireless IoT solution for industrial
tank monitoring has many advantages.
Wireless connectivity is flexible, cost-
effective, and much easier to deploy.
With a long-range and power-efficient
solution like low power wide area
networks (LPWANs), one can easily
connect hard-to-reach assets using
sensors operating on batteries that can
last for years.
Due to simple maintenance and
low device and network costs,
LPWANs can be implemented at
a lower cost than other wireless
alternatives. By unlocking 24/7 asset
visibility and feeding this data into
enterprise management systems,
a wireless IoT architecture enables
enhanced production planning, asset
management and protection, and
operational safety.
Overfilling or product discharge on
land or into water sources or into
the sea could have devastating
consequences for human life and
the environment. The charging and
discharging procedures must be
carefully supervised. Advancements
in technology have allowed the level
sensing technology to measure oil and
fuel levels in storage tanks. IoT-based
solutions are also gaining traction in
the oil & gas industry.
Step 2Accessories and Components
Senix offers a variety of displays, alarms, lights, and other accessories. The displays include panel mounted, enclosure
mounted and stand-alone models. Senix can build custom enclosures and do all enclosure wiring and display configurations
for turn-key systems ready to install and power on.
Displays & Controllers Wireless Connectivity MountingFlanges, Adapters & Brackets
Measuring to the Top of the Tank External Temperature Compensation
Senix sensors have threaded housing
and can be screwed directly to a tank
or vessel. A wide variety of flanges,
adapters, brackets, and clamp mounts
are available.
Digital controller accessories display
level measurements and/or provide
outputs to control other equipment.
Tank levels can be displayed as level
or volume in any units. Relay output
options control pumps, valves, or level
alarms. Measurements can also be
re-transmitted to additional displays
or equipment at other locations.
Other features include:
• Sunlight readable outdoor dis-
plays with large digits
• Pump control sequencing for
multi-pump systems
• Volume calculations for horizontal
cylindrical tanks or other shapes
Displays, controllers, and IoT ready
multi-variable controllers are sold
individually, with or without housings,
or Senix can custom build a packaged
system according to customer requi-
rements.
Reference Target mounted to a
ToughSonic 14 Sensor
If measuring to the very top of a tank
or vessel is desired, Senix offers a
90-degree adapter for its 1” NPT
models (ToughSonic 3 and 14). The
sensor screws into the adapter and
then the adapter screws in or mounts
to a tank. The dead band for these
two sensors is essentially inside the
adapter….so measurements can be
taken to the top of the tank. Other
adapters can be made for other
sensors as well. Senix also offers
straight adapters if a lower profile is
not needed, all intended both as size
adapters and to be able to measure to
the top of a tank.
The ToughSonic Reference Target
Temperature Compensation accessory
uses an external reference target
at the front of the sensor located in
the measurement path. Combined
with the latest SenixVIEW software,
each measurement the sensor
makes two readings; one to locate
the reference target, and one to
the distant object. Any change in
the speed of sound affects both
measurements. The reference target
location is locked during calibration,
and any change in its apparent
position is applied proportionally to
correct the distant object’s apparent
location. The result is a more accurate
measurement, unaffected by ambient
air temperature, diurnal temperature
swings, sensor self-heating, sunshine
warming the sensor, cold ambient
temperatures, or vibration.
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Senix AirWire Wireless LoRa
How Does AirWire Work?
AirWire Level TransmitterWhat Is AirWire LoRa?
Senix wireless products carry the brand name AirWire. The wireless system
described here is an emerging technology we call AirWire LoRa designed to operate
at distances up to several miles depending on terrain, antenna elevation and line of
sight. LoRa is derived from the words Long Range and handles many applications
at low power, low cost and with good range performance.
AirWire is LoRaWAN compliant for secure wireless transfers. The LoRaWAN
specification is a Low Power, Wide Area (LPWA) networking protocol designed to
wirelessly connect battery operated “things” to the internet in regional, national
or global networks, and targets key Internet of Things (IoT) requirements such as bi-
directional communication, end-to-end security, mobility and localization services.
At each monitored site, a Level
Transmitter and attached Senix
ToughSonic sensor measure the
distance down to the monitored liquid
or material. That distance is scaled and
periodically transferred wirelessly to a
Gateway that can serve many purposes,
such as presenting the level(s) in a
web page on a Local Area Network
(LAN), sending email alerts for either
high or low-level conditions, and/or
transferring the data to an external
application either locally or on the
cloud. Level can be displayed simply as
height or converted to volume (gallons,
liters, etc.). Measured data is presented
as level, volume, or percent of capacity.
The Senix AirWire LoRa System provides
a complete solution for remote
monitoring of liquid and many solid
levels. The system is available with a
variety of Senix high-quality ultrasonic
sensors. It can be used for measuring
liquid levels in tanks or storage vessels,
or a wide range of other applications. At
each site, a Level Transmitter provides
battery power to an ultrasonic sensor,
and wireless communication. Data
from the site is transmitted periodically
through a local wireless link to a
Gateway. This eliminates the need for
costly installation of electrical conduit
or cellular infrastructure and recurring
costs. The Gateway can then present
the data to other systems using the
latest IoT standard interfaces. A single
Gateway provides open, industry
standard, real-time access to the
data stream from one or many Level
Transmitters. This makes it possible to
easily integrate the data stream into
existing end user systems, rather than
forcing the user to learn a new system.
The battery-powered Level Transmitter connects with and controls a Senix RS-
485 interfaced ultrasonic level sensor, then sends each level measurement to the
Gateway. It maximizes battery life by operating for a very short period to power the
sensor and send the data, then goes back to “sleep” until the next measurement.
In that very short time, the transmitter and Gateway communicate to schedule the
next measurement and collect service statistics.
• One or many transmitters can send level measurements to one
Gateway
• Additional Gateways can be added for larger area coverage
• Attach to sensor cable or relocate to improve wireless range using
extension cable
• Small IP66 enclosure with waterproof cable entry gland
• 50-100,000 transactions using three industrial D-cell alkaline batteries
• Battery alternatives and solar versions in development
• Intended for applications with measurement rates of a few readings per hour
• Alarms - Configure dual high and dual low alarm levels and setup email alerts
when thresholds are crossed.
• Level or Volume data transmitted –Includes non-linear horizontal cylindrical
tanks. Configure the system to handle non-linear calculations like the volume
of a horizontal cylindrical tank.
• Data Storage - Add SD Card memory (where used) and setup data logging of all
connected sensors.
With AirWire Lora Technology:• Transmit tank levels inside or outdoors without installing conduit or wiring
• Collect nearby tank levels from up to several miles away
• No recurring cellular charges
• No wiring is needed at the tank site
• Uses standard Senix ToughSonic sensors
• Ideal for measurement rates as fast as a few times per hour
• Connects with any Senix ToughSonic sensor with an RS-485 interface.
Functionality
• Collect level data from monitor sites and put it to use
• Display and alert level or volume conditions
• Use in buildings or outdoors
• Real-time measurements
• 50,000-100,000 measurements on D-cell batteries
Cost Savings
• Less expensive than running conduit inside buildings
• No wiring or power needed at monitored sites
• No cellular connect charges within the LoRa network
• Reduce labor and increase safety with fewer site visits
• Upgrade to AirWire and use your existing tank sensors
Why Use LoRa?
• Relatively long range handles many nearby applications
• Very low power consumption
• Ideal for measurement rates of a few times per hour
• High Security for privacy, measurement integrity and authenticity
• Data can be restricted to company LAN or connected to cloud services
• Conforms to latest IoT standards and can integrate with existing applications
16 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 17
AirWire done with local viewing only
Monitor with LiquidLevels.com from Senix
AirWire LoRa Receiver-Gateways
Cloud-Based Monitoring
The Gateway can also post system information in the cloud. Senix offers secure Cloud-based software to monitor your tanks,
vessels, and containers remotely. LiquidLevels.com has a variety of features and there are no monthly fees. LiquidLevels.com is
a secure site to view all installed tank monitoring sensors where the status is viewed, plus users can make parameter changes to
individual tank monitors. Users with administrative access changes can be entered remotely. Tank data can be displayed in chart
form in wide or narrow time frames. Log data is available at the LiquidLevels site for download without visiting either the tank
sites or receiver gateway site. The Senix Gateways can also post data to any private address specified by the user.
All Gateways are web servers and will display an HTML webpage on the local network or on a single dedicated PC. The display
shows the latest data received from every sensor and transmitter in the system. The information includes the current tank level
or volume, system status, any alarms, battery, and RF signal level, and the date and time of the last transmission. Other screens
include specific measurement intervals, times, alarm levels, sensor information and much more. The display will show an alert if
data is overdue. The Gateway can also send an email alert of any alarm or system errors.
A Gateway accepts level measurements
from one or more level transmitters and
can:
• Act as a web server to show levels
to users on a LAN
• Send email alerts at high and/or
low-level conditions
• Inform each transmitter how
long to sleep before the next
measurement
• Log time-stamped levels for import
to Excel or other applications
• Transfer level information to other
applications either on the LAN or in
the cloud
The Basic Gateway is plastic housed
with an internal antenna and is surface,
wall or ceiling mounted. It can act as a
server and/or Ethernet gateway.
The Flex Gateway is metal housed
with a rear-attached bendable
antenna and is surface mounted. It
can act as a server and/or Ethernet
gateway, and datalog up to 22.8 million
measurements (over 10 years at 15
minutes per measurement).
to the cloud.to the cloud.
The Outdoor Gateway is sealed
in an IP67 aluminum housing with
attached antenna designed for elevated
mounting outdoors to increase system
range performance. It can act as a
server and/or Ethernet gateway, and
datalog up to 115,000 measurements
(about 20 days at 15 minutes per
measurement)). Cellular gateway
options are also available. If the level
transmitters are within range of
Public LoRa services a cloud-based
application can be used in lieu of the
Gateway. Similar or expanded features
can be provided in a cloud-based
architecture. Cloud-based services
can also be provided simultaneously
by transferring the level data stream
through the Gateway to the cloud.
Public LoRa networks are available
in a growing number of areas. If
transmitters are in public LoRa
networks, no system Gateway is
needed. Customers simply subscribe
to the public LoRa network. If the
level transmitters are within range of
Public LoRa services a cloud-based
application can be used in lieu of the
Gateway. Similar or expanded features
can be provided in a cloud-based
architecture. Cloud-based services
can also be provided simultaneously
by transferring the level data stream
through the Gateway to the cloud. The
Gateways are configured to customer-
specific needs.
18 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 19
Optimizing the Sensor for your Tank Level Application
Step 3
SenixVIEW provides an intuitive,
MS Windows interface for ease of
understanding. Target symbols,
distance data, meter and switch
symbols all show proportional, real-
time measurements. Help tips are
available by placing your mouse over
any screen element or parameter.
It is easy, it’s free and it’s all at your
fingertips. For step-by-step instructions
on using SenixVIEW, please our Video
Tutorials in the Support Center.
Information is also contained in the
sensor manuals.
Analog Output
Analog outputs are voltage or current
signals that vary proportionally
with the measured distance. Some
sensor models provide two or three
simultaneous analog outputs. The
analog distance endpoints are easily
set anywhere within the sensor’s
measurement range. Either endpoint
can be the analog high limit or analog
low limit, allowing either a positive
or negative slope. Standard analog
output value selections include 0-10
VDC, 0-5 VDC and 4-20 ma. current
loop. Computer configurable models
permit user-entered analog high limit
and analog low limit values.The figure
below shows typical analog 4-20 ma.
current loop output scaling. A target is
shown detected at about the midpoint
of the current loop analog range, which
yields a sensor output value of 12 ma.
Using Analog Outputs to Determine
Loss of Echo or Signal
If a sensor were to lose the echo off
the liquid surface for any reason, it
reacts according to its configuration.
By default, the analog outputs hold the
last value until the echo is restored.
Switch outputs also hold the status
at loss of echo. But both these are
adjustable in configuration by the user
with SenixVIEW. Analog can go to the
high or low output end of their output
range, or switches can be sent to an
active or deactivated state. Additionally,
a switch can monitor for an echo loss
and react, while the analog output
holds the last value, useful when the
analog output is part of a speed control
circuit. Senix ToughSonic sensors allow
many types of custom configuration
to do what you need. All outputs are
always available.
Switch/Relay Output
Switch outputs turn ON or OFF at a
distance setpoint and are used to
start and stop external actions or
indicators at those distances. Senix
sensors have one or two simultaneous
switches depending on the model.
Each is independently adjustable.
Computer configurable models allow
the switches to turn ON and OFF at
different distances (hysteresis) or to
be ON or OFF only when a target is
within a specified switch window. The
hysteresis feature allows a single sensor
to perform a complete control function,
such as turning a pump on at a low
level and off at a high level to maintain
a liquid level within limits
The switch window feature allows
proximity sensing only within specific
distance ranges. A single switch output
can perform a control function such
as managing the liquid level in a tank
by turning a pump or valve on or off at
specific levels.
Using SenixVIEW software, switch
functions and responses can be
optimized using adjustable ON and OFF
time delays, initial power-up states,
hysteresis and window modes, and
loss of target states with an associated
time delay. Each switch output can
be set to “NPN” type (sinking) or
“PNP” type (sourcing) for universal
compatibility. Some switch features are
also adjustable using the “teach” push-
button.
Manage Sensor Configurations
Use SenixVIEW to manage sensors by
saving configuration files along with
notes about the setup. Commission
new sensors by cloning configuration
files in a few seconds without the need
for recalibration. Easily distribute
configuration files among facilities and
colleagues.
Sensor Analysis
SenixVIEW allows you to view real-time
output using a variety of statistical
and display tools. Fine tune sensor
performance in real time. Create time-
stamped data logs and export them
to Excel to view application data over
time. You can even use your ToughSonic
sensor to system test the rest of your
connected equipment virtually.
Sensor Setup (Configuration)
SenixVIEW allows you to access nearly
80 functionally organized parameters
that affect operating range, sensitivity,
measurement rates, outputs, output
filters, condition responses and more.
Sensor changes are stored in the sensor’s
non-volatile memory when power is off.
As many setups as you want can also be
stored for later recall to create an exact
copy in a new sensor for maintenance or
OEM product duplication.Do I need a computer to use
these sensors?
Absolutely not! The pushbutton TEACH
features provide all the functionality
many users require.
Many Senix sensors include Push
Button TEACH capability. This allows
calibration using actual targets for
quick and easy setup. There are no
touchy potentiometers to adjust,
and pushbutton security features
are provided to prevent accidental
misadjustment. The TEACH features
also provide many pushbutton-selected
features that give our sensors increased
flexibility.
Senix ToughSonic sensors are ready to go at shipment but offer ease of customization. A quick and simple set-up can be
accomplished through Senix’s Push Button TEACH technology. If the tank level application requires other optimization,
SenixVIEW software is used to set outputs, set span and slope, set dead band to suit application, set filters to overcome motions
or interferences, set event responses using delays, build a sensor network, and more.
The computer configurable sensor
models, however, offer greater
ease of use, feature flexibility and
application visibility that many users
find essential. The features provided
by our SenixVIEW™ software would not
be possible without a computer. Once
an installation setup is determined, it
can be stored and duplicated easily and
quickly using the computer, or Senix
can provide sensors pre-configured to
your exact needs. Once a sensor has
been selected, as well as any needed
accessories, the next step is setting up
your sensor an optimize them to your
application.
SenixVIEW ultrasonic sensor
configuration and analysis software
is included with every ToughSonic
General Purpose and ToughSonic
CHEM sensor, giving you total control
over all sensor features and functions.
Calibrate and optimize Senix sensors
with a few keystrokes to yield better
understanding and performance of
your applications.
20 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 21
Ingress Ratings
Our ToughSonic line is IP68 / NEMA-4X
/ NEMA-6P rated and will operate after
complete submersion.
Outdoor Environments
The ToughSonic models are designed
to withstand the harshest outdoor
environment with full epoxy potting,
UV shielded cables and stainless steel
or polymer housings. The sensor face
must be protected from buildup of
ice, snow, mud and other debris or the
transmission of sound energy will be
reduced or blocked.
Temperature
Senix ToughSonic sensors have built-in
temperature compensation for the
change in the speed of sound in air.
This compensation is usually based
on an internal temperature sensor
deep inside the sensor itself. The
sensor should be kept from direct
sunlight or heat sources if temperature
compensation is being used, because
artificial heating of the sensor can
influence the measurements. Senix
offers an external temperature
compensation option that is not
affected by sensor heating, rapid
temperature changes day to night, or
internal self-heating. The temperature
of the air between the sensor and
the target can affect measurement
accuracy since the speed of sound
How wide is the ultrasonic beam?
The ultrasonic beam angle in Senix®
sensors is typically 10-15 degrees and
conically shaped. The ultrasonic beam
varies slightly by specific sensor and
detailed on our data sheets. The real-
world response to an off-angle target
has a lot to do with the target size and
orientation, and the sensitivity setting
of the sensor. Computer configurable
sensors can be adjusted to optimize
detection of the desired target and
ignore undesired targets.
What happens if the ultrasonic beam
hits other objects?
A common misunderstanding is that
if the ultrasonic beam is larger than
the target there is a problem. This is
not true in general. It does not matter
that the beam is larger or reaches
other objects if those objects do not
reflect sound back to the sensor or
are farther away than the target of
interest. For example, this means that
a sensor can be mounted next to a wall
or can measure inside a tube and the
measurement will not be affected if the
wall or tube surface is smooth because
no sound energy is reflected to the
sensor from the surface. With Senix
sensors, the detection of undesired
or off-axis objects can be measured
by adjusting beam width, sensitivity
adjustment, range adjustment,
processing filters and object masking.
connected to a Modbus addressable,
multi-drop wired network. It is more
robust than RS-232 and allows far
longer communication distances.
Senix ToughSonic sensors can
also send unidirectional ASCII
characters (“ASCII streaming”) after
each measurement, useful in some
applications. Communications baud
rate is adjustable from 9,600 to 115,200
baud and proprietary features are
available for high-speed data collection
in multi-sensor applications.
Mounting ultrasonic sensors
The following general sensor mounting
guidelines should be adhered to. For
more complex mounting guidance,
please contact Senix Customer Service.
• Ultrasonic sensors should be
mounted in plastic threaded
adapters to avoid acoustic energy
absorption through the sensor
body.
• Sensors should be hand tightened
only. Never apply a wrench to the
sensor body.
• When tank mounting to a domed
or round tank, adjust the sensor
mount until the transducer face is
square with the target surface.
• Mount the sensor directly to the
tank ceiling at a flange opening.
If a riser is added, it must be of
sufficient diameter to cause no
inner wall reflections. Round off
the lower edge of the riser.
• Provide a sunshade for outside
installations to prevent the sensor
body from overheating and causing
erroneous measurements. The
sensor body should stay equal to
the ambient air temperature so
the sensor’s built-in temperature
compensation can work correctly.
varies with temperature. If this is an
issue, temperature compensation is
available in all computer configurable
models. The speed of sound changes
approximately 0.175%/°C, or 1%
for every 5.7 °C. As the temperature
increases the target will measure closer,
and vice versa.
Humidity
Humidity change is generally not a
significant factor (0.036% / 10% RH
change).
Pressure/Vacuum
Normal atmospheric pressure
changes or small pressure changes
in vessels will not affect ultrasonic
sensor operation. Ultrasonic sensors
are not designed for high pressure
applications, although Senix sensors
have proven to work fine at pressures
<100 psi. With respect to a vacuum,
sound does not travel in a vacuum and
therefore the sensors will not work in a
vacuum environment.
Ultrasonic Noise
Locally generated ultrasonic noise at
the sensor operating frequency can
interfere with measurements. Some
potential sources are high pressure air
releases near the sensor caused by air
nozzles, pneumatic valves or solenoids,
How do I maintain my Senix®
ultrasonic sensors?
Senix sensors are housed in rugged
materials and fully potted in epoxy
resin. It is important to keep the
ultrasonic transducer face clear of
ice, snow, dirt, and other physical
barriers to prevent disruption of the
ultrasonic signals. Ideally, sensors
will be mounted with transducer
faces pointed downward to minimize
material collection on the face. If
transducer faces do require cleaning,
pressurized air can be used. In
liquid level applications, occasional
submersion or spraying of the material
being measured is often sufficient
to maintain a clean transducer face.
Sensors with exposed transducer faces
can also be cleaned with alcohol or
window cleaner, if necessary. DO NOT
use solvents such as MEK or acetone
on ToughSonic sensors with exposed
transducers.
How accurate are Senix® Ultrasonic
sensors?
ToughSonic 3, 12, 14 and the
ToughSonic CHEM 10 and CHEM
12 models have a measurement
resolution of 0.086 mm (0.003384
inches). The ToughSonic CHEM 20 has
a measurement resolution of 0.172 mm
(0.0068 inches) and the ToughSonic
CHEM 35 has a measurement resolution
of 0.3438mm (0.0135 in.)
Other measurement, environmental
and target factors affect the overall
result. Typical repeatability is better
than 0.5%, and accuracy is <2% of the
measured target distance.
and ultrasonic welders. In computer
programmable sensors, processing
options can be selected to ignore the
effects of noise bursts. Higher frequency
sensors are less susceptible due to
sound absorption in the air. Air paths
are usually rearranged, blocked, or
eliminated to prevent this. Senix sensors
are designed to allow several ultrasonic
sensors in the same vicinity without
mutual interference.
Audible Noise
Loud audible noises produced by
machinery do not affect the sensor.
How do I know what the measured
distance is?
Senix sensors provide the measured
distance in several analog and serial
data formats. Sensors can have one
or more simultaneous outputs in
various combinations for connection
to displays, Programmable Logic
Controllers (PLC’s), computers, motor
drives − almost any type of electronic
equipment.
Serial Data
All Senix sensors have either an RS-232
or RS-485 serial data interface that uses
either the industry standard Modbus
protocol or a simpler ASCII streaming
output. Modbus allows two-way
communication of control instruction
and data transfer. SenixVIEW
configuration software uses Modbus
for sensor configuration, monitoring
sensor performance, and testing.
Serial RS-232 is an electrical interface
for single sensor communication
with computers, displays or other
user equipment over relatively short
distances. Serial RS-485 interface
allows multiple ultrasonic sensors
and other RS-485 devices, such as
numeric displays, PCs, or loggers, to be
Senix ToughSonic Ultrasonic Sensor FAQs
22 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 23
Small vs. Large Tank
Sensors in a closed space like a tank
are usually run at a slower rate (i.e.,
longer interval between measurements).
This allows sufficient time for acoustic
energy to dissipate in the closed space.
An interval of no less than one second
is often recommended to avoid this
interference. Sensors installed in a
standpipe or stilling tubes likewise have
a slow dissipation so they should be
slowed. Senix products include a special
sensitivity setting for stilling tubes that
more closely matches the dissipation
rate occurring in that environment.
Filtering
If a tank is subject to waves from agitators or from infall or pumps, With SenixVIEW, all Senix ToughSonic sensors can utilize one
of several filters to mitigate the jittery readings they produce. Available filters include stability test, averaging type, and delayed
reaction types. Often a simple running average of the previous 25 measurements or so gives proper smoothing of otherwise jittery
data, and the data comes from the sensor at its configured running rate.
Input Rejection Filtering precedes any averaging filtering. Input rejection filters ignore some measurements. The input to these
filters is the raw sensor distance measurement. The output (“Good” data) is then input to an averaging filter (if used). For example,
the sensor can be configured to reject all except the closest measurement, or all but the farthest measurement. Examples include
maintaining a measurement value of a poor target (weak or intermittent echo). This filter is useful to ignore an unintended or
unwanted target that occasionally passes between the sensor and the intended target. Examples include ignoring mixer blades in
tanks, ignoring traversing objects not the intended target, or rejecting sporadic interference (electrical, physical, or acoustic).
Averaging Filters receive their distance data from the input rejection filters. The averaging filter response time is therefore affected
by the rejection filter selections. If an unstable target is detected by the stability filter (x of y), the averaging filter and subsequent
processing are suspended at the current distance until stability returns.
Tank Mounting
Tank sensors should be mounted in
the vertical to receive ultrasonic echos
from the liquid surface even from a
near empty tank. A sensor mounted
on a sloped tank roof or domed tank
must still be mounted vertical. The
greater the measurement range the
more critical this alignment is. All
Senix ToughSonic sensors are threaded
in order to be screwed into a tank or
vessel, and Senix also offers a variety
of flanges, mounting options and
adapters for a range of threaded hole
diameters and configurations.
Foam, Turbulence, and Condensates
Foam or Condensation created by certain liquids can partly absorb an ultrasonic
signal. Turbulence can deflect an ultrasonic signal. There are several possible
techniques for addressing these issues when using an ultrasonic level sensor for
tank level measurements.
1. Install a standpipe
Also referred to as a Stilling Tube, a Standpipe is often used to separate surface
foam, dampen turbulence, or maximize the acoustic signal strength of the level
sensor. Although frequent cleaning may help, it is not generally recommended to
use a standpipe in applications with dirty, coating or scaling liquids that will leave
material build-up on the inner pipe wall.
The standpipe must be one continuous section of smooth pipe without any breaks or
transitions. The inner diameter of the pipe must be greater than the sensor surface
O.D, and preferably the level sensors beam width. The latter may not be practical
depending on the size of the tank and distance measured, so it is important to have a
standpipe that will reflect ultrasonic signals and have a smooth surface.
It is also recommended to have at least one vent hole and preferably within the
sensors dead band. The pipe should extend to the bottom of the tank, or at least
below the level sensor’s measurement span, and have a 45º angle on the bottom of
the pipe, and the level should always be maintained above the cut.
2. Maximize Range and Power
As with foam and some condensates, powder products are absorbers of acoustic
energy. In addition, dry materials in silos present smaller target surfaces that are
often not level or simply absorb most of the sound energy. We recommend using a
longer-range sensor product for the additional power they provide in those cases.
Also, it may be necessary to point the sensor out of the vertical depending on the
angle of repose of materials in a silo as it is both filled or drawn down. A better
target strength may be possible with careful sensor positioning.
Multi-Sensor Wired Connections:
Networks and Synchronization
Senix ultrasonic sensors can be
connected in multi-sensor data
networks to retrieve measurements
and/or adjust sensors using SenixVIEW
software. An entire collection of data-
networked sensors can be managed,
stored, and retrieved using a SenixVIEW
feature called Group Control that
permits the entire collection to be
backed-up, restored or duplicated
quickly. Multiple sensors can also
be connected for synchronization
(SYNC) to prevent crosstalk or assure
simultaneous measurements. The data
networking and SYNC functions are
mutually exclusive, but generally serve
different purposes.
Sensor Data Networks
• Data networks are created by wiring
two or more ToughSonic sensors in
a multi-drop configuration
• Sensors can be any RS-485
model type, but all must have
independent addresses and use
the same baud rate
• Sensors in continuous mode will
update analog and switch outputs
independent of the network
requests
• Sensors in polled mode will only
measure and update outputs upon
receiving a network request
• A 4-wire data cable can supply both
data and power to the sensors,
or sensors can instead be locally
powered
Sensor Synchronization (SYNC)
Sensors in close proximity in an open
setting may interfere with nearby
sensors. Senix sensors offer SYNCH,
a full featured method of controlling
sensors measurement sequence or
groupings.
Multiple sensors can be connected for
synchronization to prevent crosstalk or
assure simultaneous measurements.
A typical application is to prevent
two sensors in close proximity from
interfering with one another, common
on converting machinery and profiling
applications.
SYNC networks are created by wiring
the yellow and gray communications
wires of all sensors together (see
diagram). Operating SYNC groups
cannot simultaneously act as a data
network.SYNC consumes the serial data
port and assumes the sensor’s analog
and/or switch outputs are used.
• One sensor is selected as the group
Master and the remaining sensors
as Slaves (up to 31)
• Selection is made using wither the
Teach pushbutton or SenixVIEW
software
• The Master can have between 1 and
5 “phases”, and its Measurement
Interval determines the phase timing
• Sensors measure simultaneously,
sequentially, or in groups
depending on their phase
configuration
• Slave sensors that lose their SYNC
input have configurable analog and
switch “Loss of SYNC” responses
24 / Ta n k Le ve L Mo ni Toring guide Tank Leve L MoniToring guide / 25
Accuracy & Temperature Compensation Accuracy specifications are generally
determined indoors, in a controlled
lab environment, and under constant
temperature and fixed conditions and
with no interference from factors such
as wind or air movement, etc. Generally,
specifications such as Accuracy are used
to compare one sensor to another.
Accuracy, or absolute accuracy is the
difference between the output value
that is measured by the Ultrasonic
sensor, and the actual target distance.
For example, an ultrasonic water
level sensor reading a full-scale range
of 12 feet or 144 inches will have an
accuracy of ±0.144 inches (at ambient
temperature and controlled conditions).
The same sensor reading a distance
of 75 inches will have an accuracy of
±0.075 inches. This 0.1% detected
accuracy is applicable whether the
sensor is reading in distance level/
volume (gallons).
AS mentioned earlier, the performance
of an ultrasonic sensor depends on
several physical parameters. For
temperature, there are several options
available to improve accuracy.
The following shows a Senix ToughSonic
CHEM sensor measuring outdoors with
fluctuating temperature. The Orange
is the temperature of the sensor that
is changing by as much as 5-6 degrees
Fahrenheit. The Red shows the
distance measurement fluctuating with
temperature by at least 3-4 inches. The
Green line is the distance measurement
with temperature compensation turned
on in the sensor and measurements
much more stable and consistent.
Air temperature has the greatest
impact on the measuring accuracy
of an ultrasonic sensor. Temperature
fluctuation affects the speed of an
ultrasonic sensors pulse or sound
waves. As temperature increases, sound
waves travel faster to and from the
target. Even though the target has not
likely moved or shifted, it will appear
that the target is closer.
A more detailed explanation is that
after the transit time of the reflected
ultrasonic pulse has been measured,
the sensor calculates the distance to
the object using the speed of the sound.
When sound is propagated in air, the
speed of sound is about 344 m/s at
room temperature. However, the speed
of sound is temperature-dependent and
changes by approximately 0.17% with
each degree Celsius. These changes
affect the transit time and can distort
the calculated distance. Without
temperature compensation and at a
measuring distance of 100 cm, a 20° C
change in temperature would cause a
measurement error of -8.5 cm at 70° C
and +7.65 cm at -25° C.
Most ultrasonic sensors by Senix have
a working range of -40° C to +70° C, and
all ToughSonic ultrasonic sensors have
an internal or embedded temperature
sensor to compensate for this effect.
This internal sensor measures the
sensor body temperature, and the
sensor corrects the temperature-related
distortion of the measured values (see
temperature compensation). Internal
temperature compensation sensors
do have limits, however. An internal
temperature compensation may also
be affected by external heating or
cooling sources as they cannot adjust to
extremely rapid changes well, plus they
may not be close to the temperature
in the actual measurement path such
as inside an enclosed silo, tank or
container.
The following shows a Senix ToughSonic
CHEM sensor measuring outdoors with
fluctuating temperature. The Orange
is the temperature of the sensor that
is changing by as much as 5-6 degrees
Fahrenheit. The Red shows the
distance measurement fluctuating with
temperature by at least 3-4 inches. The
Green line is the distance measurement
with temperature compensation turned
on in the sensor and measurements
much more stable and consistent.
Air Temperature
For even more severe changes in air
temperature that require an even
faster response, Senix has developed
the ToughSonic RTTC system that
overcomes the time lag inherent with
a built-in sensor and offers customers
with an improved compensation option.
ToughSonic Reference Target
Temperature Compensation accessory
uses an external reference target at
the front of the sensor located in the
measurement path. Combined with
the latest SenixVIEW software, for each
measurement the sensor takes two
readings; one to locate the reference
target, and one to the distant object.
Any change in the speed of sound
affects both measurements. The
reference target location is locked
during calibration, and any change
in its apparent position is applied
proportionally to correct the distant
object’s apparent location. The result
is a more accurate measurement,
unaffected by ambient air temperature,
diurnal temperature swings, sensor
self-heating, sunshine warming the
sensor, cold ambient temperatures, or
vibration. Field calibrations can be done
at any time or temperature.
The two illustrations below show side
by side sensors operating over a canal,
one with conventional temperature
compensation and one with RTTC
compensation. In the conventional,
notice the apparent canal depth varies
with the extremes of temperature, while
in the RTTC plot notice the apparent
distance is unaffected by temperature
diurnal swings. The temperature effects
have been largely eliminated.
Diurnal temperature swings can be
ignored, and external heating or cooling
of the sensor will not result in incorrect
distance or level measurements. The
sensor could be exchanged on site and a
new calibration could be done on site at
any temperature.
The RTTC accessory will improve the
sensor’s performance in conditions with
significant changes in temperature due
to diurnal affects. The intensity of the
diurnal changes and how the sensor
software is set up will affect the sensor’s
ultimate performance.
External Reference Targets
The illustration above shows a canal
level that appears to vary as the air
temperature fluctuates over several days.
The untrasonic sensor uses a conventional
method of termperature compensation.
At higher temperatures, the canal surface
reas closer and plots as deeper water. The
clip is seen from a control gate opening.
Sensor with Reference Target Temperature
Comensation (RTTC).
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2:2
0:06 A
M
8:2
0:07 A
M
2:10:
07 P
M
8:00:
07 P
M
1:5
0:09 A
M
7:4
0:09 A
M
1:30:
10 P
M
7:21:
08 P
M
1:1
0:11
AM
7:0
0:12 A
M
12:
50:
13 P
M
6:40:
13 P
M
12
:40:
00 A
M
6:3
0:01 A
M
12:
20:
02 P
M
6:10:
02 P
M
12
:00:
02 A
M
5:5
0:04 A
M
11
:40:
04 A
M
5:30:
05 P
M
11:2
0:06 P
M
5:1
0:07 A
M
Internal Temperature Compensation
Inches Uncomp Inches Sensor Temp (°F)
10516 Route 116, Suite 300
Hinesburg, VT 05461 USA
Ph: 802-489-7300
Fax: 802-489-7400
About Senix Corp
www.senix.com
Senix designs and manufactures advanced ultrasonic sensors for level
measurement, distance ranging and object detection. Senix ToughSonic®
sensors are used in a wide range of automation and research applications
worldwide. Our sensors are used in a broad array of industrial and
scientific applications, including machine and motion controls, web
controls (material loop and roll diameter), liquid level measurement, water
measurement and control such as in farming and agriculture applications,
person/object proximity sensing – virtually any place where non-intrusive
measurement and feedback are desired. The company transformed
non-contact distance measurement in 1990 with the world’s first user-
configurable ultrasonic sensor and has been pushing the boundaries of
sensor intelligence and ruggedness ever since. Senix Corporation is a
privately held company located in Hinesburg, VT, USA.